1. Technical Field
The present invention relates to an imaging apparatus, a radiographic imaging apparatus, and a radiographic imaging system. More specifically, the present invention relates to an imaging apparatus used in a radiographic imaging apparatus and a radiographic imaging system, which is suitable for use in still image radiography such as general radiography or moving image radiography such as fluoroscopic radiography in medical diagnosis. Note that, in the present invention, the term radiation includes, in addition to α rays, β rays, γ rays, which are beams of particles (including photons) emitted by radiation decay, beams having energy higher than or equal to that of the above rays, for example, X-rays, particle beams, cosmic rays, and others.
2. Background Art
In recent years, radiographic imaging apparatuses including a flat panel detector (hereinafter abbreviated as FPD) formed of a semiconductor material have begun to be put into practice as radiographic apparatuses used for X-ray medical diagnostic imaging or non-destructive inspection. Such radiographic imaging apparatuses are used as, for example, in medical diagnostic imaging, digital imaging apparatuses for still image radiography like general radiography or moving image radiography like fluoroscopic radiography.
In such radiographic imaging apparatuses, as disclosed in PTL 1, the ability to switch between an area (field-of-view size) that is read by an FPD and a radiation area of X-rays has been studied. However, in a case where switching is performed so as to increase the radiation area, the sensitivity or dark output of pixels differs between the irradiated area and the non-irradiated area of the FPD. Thus, a ghost (image step), which is affected by the radiation area, occurs in an obtained image, leading to the risk of reduced image quality.
In PTL 2, an examination is made of performing image processing for correction on such a ghost that is affected by the radiation area. Specifically, required ghost correction coefficients are obtained for each X-ray irradiation condition on the basis of data that includes a ghost and that is obtained by uniform irradiation, the ghost correction coefficients corresponding to X-ray irradiation conditions under which data regarding the part being examined, which is the radiation area, is collected and the time taken from the start of X-ray irradiation. Thus, the data regarding the part being examined is corrected using the required ghost correction coefficients, and corrected image data is generated.
In the correction technique of PTL 2, however, since the correction is performed using image processing, the management of parameters or correction processing is complicated and the complexity of the overall apparatus increases. In addition, complex operations such as acquiring data in advance for correction are required, and also strict management such as thoroughgoing data sampling is required to obtain stable image quality. Further, the number of afterimages included in an image signal obtained from the FPD, which may cause the ghosts described above, is not reduced, and therefore it is difficult to obtain optimum effects in various situations.
Citation List
Patent Literature (PTL)
PTL 1: Japanese Patent Application Laid-Open No. 11-128213
PTL 2: Japanese Patent Application Laid-Open No. 2008-167846